Polyvinylbutyral (PVB) sheeting is widely used as an interlayer for laminated safety glass. Typically, the polyvinylbutyral is used in combination with one or more layers of glass to provide a composite which is resistant to shattering. The polyvinylbutyral generally contains a plasticizer to provide a balance of mechanical properties satisfactory for the subsequent handling of the sheeting and performance in a laminar structure. In addition, the polyvinylbutyral sheeting often contains an adhesion control agent to provide a desirable balance between the energy absorbing function of the polyvinylbutyral on impact and adhesion needed to prevent broken glass from being detached from the interlayer when the laminate is broken.
A wide variety of adhesion control agents has been suggested for use with polyvinylbutyral sheeting. However, certain plasticizers used in PVB, including triethylene glycol di-n-heptanoate (3G7) and tetraethyleneglycol di-n-heptanoate (4G7) are usually hydrolyzable. Accordingly, when these plasticizers are incorporated into PVB, the acid concentration of the blend increases markedly with processing. Under these conditions, many adhesion control additives previously suggested for use with PVB are ineffective in providing the desired characteristics in the final product.